BACKGROUND Magnetic resonance imaging (MRI) of osteoarthritis (OA) of the knee is a preoperative method of joint assessment. Histology of the joint is invasive and performed after surgery. T1rho/T2 MRI mapping is a new preoperative method of quantifying joint changes. This study aimed to analyze and compare the histological changes in the joint cartilage with the use of quantitative T1rho/T2 MRI mapping in patients with OA of the knee. MATERIAL AND METHODS Twenty patients with OA of the knee (20 knees) underwent preoperative MRI with T1rho mapping, T2 mapping, T1-weighted, and T2-weighted fat-suppressed MRI sequences. The degree of OA of the knee on MRI was graded according to the Osteoarthritis Research Society International (OARSI) criteria and the Kellgren-Lawrence grading system. Histological grading of OA used the OARSI criteria. Four tibiofemoral condyles were assessed histologically, and the degree of cartilage destruction was determined using the OARSI criteria. Two investigators performed cartilage segmentation for T1rho/T2 values. RESULTS Histology of the four knee joint condyles confirmed mild to severe OA. The histology of the cartilage thickness (P<0.001) and the MRI findings of the distal medial condyle (P<0.00) were significantly different from the other three knee joint condyles. The T2 and T1rho values of each condyle were significantly correlated with the histological grade (II-IV) of the joint condyles, including the cartilage volume, cartilage defects, thickness, and bone lesions (P<0.05). CONCLUSIONS In 20 patients with OA of the knee, preoperative T2/T1rho MRI identified Grade II-IV OA changes in the joint.